Isotachophoresis (ITP) is an established technique for analyte preconcentration and separation in which ions form discrete and contiguous zones between a fast leading electrolyte (LE) and a slow trailing electrolyte (TE). Analyte detection methods in ITP are either direct or indirect. Direct methods sense analyte molecules with (typically) UV-absorbance, electrochemical, or fluorescence detection. Indirect methods sense surrogate physicochemical phenomena (e.g., local temperature or electric field) affected by the analyte. Analytes have been indirectly detected through quenching of a fluorophore in micellar electrokinetic capillary electrophoresis, and through displacement of UV- or fluorescence-detectable background ions in capillary electrophoresis (CE). In US 2008/0197019, Khurana and Santiago describe a detection scheme which detects ITP analyte zones indirectly by imaging “gaps” in the signal of fluorescent mobility markers that form as the mobility markers focus.